LOCK: size

[antbryan]

http://www.ietf.org/mail-archive/web/ftpext/current/msg00453.html

"I think it would be useful to have an alternative to "boundary" called "size", that could provide the size of the raw data for binary transfers. That might provide quite a performance advantage compared to having to search for the boundary."

[antbryan]

we could have boundary REQUIRED and size RECOMMENDED or boundary or size REQUIRED?

[bagder]

I agree that sending data in a chunked-encoding style (from HTTP 1.1) is much easier for both sender and receiver instead of having to check for a boundary separator in the stream.

It would be good to get an FTP server author's point of view on this.

[antbryan]

the original comment & this one from another person were from the makers of CompleteFTP http://enterprisedt.com/products/completeftp/overview.html

"I just wanted to back my colleague, Bruce, on the performance issue related to detecting boundaries. A few weeks ago I wrote code that detects MIME boundaries in HTTP-POSTs while piping the data to a file. The best I managed to achieve was significantly slower than simple piping. I therefore think that optionally including the size is important for performance."

[hashbackup]

I think when LOCK is used, an easy way to handle this for binary files is to add the file size as a 1xx response to RETR and not use boundaries. So for a 100,000 byte file:

C> LOCK
S> 200 OK
C> RETR myfile
S> 1xx 100000
S> (100000 bytes of data from myfile)
S> 200 OK

For STOR, the same mechanism could be used:

C> LOCK
S> 200 OK
C> STOR myfile
C> 1xx 100000
C> (100000 bytes of binary data)
S> 200 OK

Or, the size of the file could be given with the STOR command after the filename. This could also be done with RETR, but a SIZE command would be necessary first so that the client knows how big the binary read will be.

For text transfers, the size of the file on disk may not be the size of the transfer because of different newline handling on Windows (2 chars vs 1 on Unix). So for text transfers, boundaries are better.